I look at it this way:
Trivex for it's mechanical properties: drills on low to medium power lenses.
Trivex for its optical properties: people who are sensitive to chromatic aberration who's job can't be done in CR39 (very rare).
Other than that, trivex is not "needed" (but is a great lens).
1.67 is the "high" high index that we use. You can drill it. It's expensive but not crazy like 1.7+ indices. It's available in a jillion designs.
1.6 is a "tweener" for me, and though I'm emotionally attached to it, I never use it because:
Polycarbonate is great for just about everyone else. Any abbe issues (which are extremely rare, IMO) are very power-dependent, and if you switch up to 1.67 you have the same issues.
So:
Polycarb for everyone
1.67 for the super-myopes or for the moderate power lenses in rimless
1.5 for picky or cheapies
1.53 for low power rimless or pickies that need a semi-rimless.
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